Pulverizing mill



3- w. MJS HELD ON 2,319,192

' PULVEEIIZINGMILL Filed July 21, 1941 2 Sheets-Sheet 1 v I INVENTOR.

- AHORNEY y 1-1, 1943- w. M. SHELDON 2,319,192 v PULVERIZI-NG MILL Filed July 21, 1941 2 Sheets-Sheet 2 INVENTOR.

A. ATTORN Y 1 line I-l oflig. 2; V V 'Fig. 2 is a sectional view taken on line 1-2 of Fig. 1;

; Patented May 11, 1 943 2,319,192 v r runvamzmemnm wanna M. Sheldon, Elisabeth, N.J., asslgnorto Louis Ruprecht MontcIaIr, N. J.

Application July 21, m1, ser al-Names: A V

'6Ciaims.(Cl.8311) This-invention relates to pulveri'zing mills of the rotary beater, or hammer, type, that is. mills in which a high speed rotor having'a plurality of circumferentially spaced hammers, or beaters, is mounted in a mill chamber a lower portion of the peripheral wall of which is formed'by a screen or is otherwise provided with suitable openings for the escape of the pulverized material. More particularly, the invention relates to means whereby the material to be pulverized be given by a detailed description of a pulverlzing mill embodying the invention in the form now considered best, and such a description will now be given in connection with the accompanying drawings illustrating such a mill, in which: Fig. 1 is a sectional view of themill taken on the air inlet passage being substantially larger than the discharge opening" and spaced away from the hopper bottom sumciently to permit the Fig. 3 is-a perspective view of the material feeding means: and V Fig. 4 is asectional viewillustrating an alternative form of feeding means intended especially for feeding material of relatively high density.

Referring first to Figs. 1, 2 and 3, the drawings I 7 'show a hammer mill of well-known form having a cylindrical mill chamber ll formed by a casing the peripheral wall or which is imperforate except' for a lower perforate portion, 'or screen, I!

'i'or the. escape of the'pulverized material. A

high speed rotor Ills mounted in the mill cham ber carried. by a shaft ll extending; through 'bearings'in' aghousing it and which carries a pulley for a belt I! by which the shaft is rotated at high speed "from a suitable motor. The rotor i has the usual pivotally. mounted circumferen- -tially spaced hammers, or beaters, IS. The material to be pulverized enters the mill chamber through a feed opening in the end wall 2| of a flat or slightly coned bottom 21 having a discharge opening 28 therein. An air inlet passage ll is provided opening downward directlyover the discharge opening 28, the outlet opening of stops this flow of material to the mill chamber The air pipe is most desirably a material to pass beneath it. Most desirably, the air inlet pa'ssageis provided by a pipe 3| extending vertically downward within the hopper.

The air inletpipe I] is raised from the hopper bottom sufliciently to permit the material, when the mill is not in operation, to flow inward beneath the lower end of the pipe a short distance determined by its natural angle of repose,'indicated by dotted lines in Fig. 1. The size of the pipe end with relation to the size of the discharge opening" is such that, if the pipe end is not spaced too far from the hopper bottom, a line from any point on the bottom edge of the pipe defining the angle of repose of the material will not pass through the discharge opening. Consequently, under static air condition no material will flow out through the discharge opening. When the mill is inoperation, however, the rotor, acting as a suction fan, induces a strong current of air to flow down through the pipe3l'and through the discharge opening 28 and the closed passage 28 and through the feed opening 20 into the'mili chamber, and this air, current as it flows against and past the material beneath the end of the air' inlet pipe sweeps material from the mass standing at its angle of repose and carries it inward and down, through the discharge openchamber. The material will thus be fed into the mill chamber at a controlled rate so'iong as the supply of material is maintained in the hopper and thejmill is in operation; and when the mill also stops.

' straight cylindrical pipe as shown, but, whatever its shape,'itfshould be of suiiicient cross-sectional size'in all partsto avoid retardation of the air flow by reason ofskin friction.

'I'he'rate at which the. material i'sfied to a min exerting a given suction from ahopper having a .discharge opening of a given size and an air inletpipe with a bottom or outlet end of a given'size will depend on the spacing of the lower end of the air inlet pipe from the hopper bottom and may be varied within the feed range of the apparatus by raising'o'r lowering the pipe. The air inlet pipe is therefore most desirably made vertically adjustable. For this purpose as shown, the air inlet pipe is mounted to slide within a supporting sleeve 35 fixed within the hopper and is supported in the sleeve by means of a stud or pin 38 extending from'the pipe and resting on the upper edge of the sleeve which is shaped as a stepped cam 31. V

For the feeding otcomparatively high density materials, such as lead sulphide in V4" and smaller pieces, it is better to have a restricted annular outlet opening at the lower end the air pipe in order to cause the air to how against the material at a higher velocity than it does when the pipe has an unobstructed open end. As shown in Fig. 4, the air pipe is provided with a restricted annular outlet opening by having a deflector ll mounted centrally within the outlet end or the pipe. This deflector should be of a shape to avoid the causing of eddy currents and resulting flow resistance, and a conical deadiustable has been found entirely suitable. v The new mill may be used to advantage for grinding orpulverizing all kinds of dry material in individual pieces or in granular condition, provided theniaterial is not tacky-or gummy; It has been found especially suitable for light materials such as wheat, oat, corn, buckwheat, rye

.and barley grains, split peas, and granulated the air pipe.

What is claimed is: a l. The combination with a pulverizing mill comprising a high speed rotor having a plurality I o! circumierentially spaced 'beaters mounted within a chamber having asuction feed opening adjacent the axis of rotation oi the rotor, of means for supplying material to be pulverized to the feed opening of the mill at a controlled ratecomprising a hopper for receiving the material to be pulverized having a bottom with a discharge openingtherein, means providing a suction passage leading from said discharge opening to saidsuction feed opening, and means providing an air inlet pipe extending into the hopper the outlet end 0! which is substantially larger than said discharge opening and is positioned directly over said discharge opening, and spaced from the hopper bottom sumciently to permit material to pass beneath it. v

2. The combination with a pulverizing mill comprising a high speed rotor having a plurality of circumferentially spaced heaters mounted within a chamber having a feed opening adjacent the axisof rotation of the rotor and havingoutlet openings in its peripheral wall for the discharge of the pulverized material; of;means for supplying material to be pulverized to the feed opening of the mill at a controlled rate com-v prising a hopper for receiving the material to I be pulverized'having a bottom with a discharge feed opening of the mill chamber, and means providingan air inlet pipe'extending into, the

hopper the outlet end of which is substantially largerthan said discharge opening and is positioned directly over said opening and spaced item the hopper bottom suiflciently to permit material to pass beneath it.

flector, as shown, mounted so as to be vertically of circumierentially spaced 'beaters mounted. within a chamber having a feed opening adia- 3. The combination with a pulverizing mill comprising a high speed rotor having a plurality of circumierentialiy spaced beater-s mounted within a chamber having a feedopening adjacent the axis of rotation of the rotor and having outlet openings in" its peripheral-wall. for the escape of the pulverized material; of means for feeding material to be pulverized to the mill chamber at a controlled rate comprising a hopper for receiving the material having a bottom with a discharge opening therein, an air inlet pipe extending downward within the hopper, the open lower end or said pipe being substantially larger than said discharge opening and being directly over the opening'and spaced from the hopper bottom sufliciently to permit the material to pass beneath it, means for adjusting said pipe toward and from the. hopper bottom, and means providing a suction passage leading from the discharge opening or the hopper to the feed opening 01 the mill chamber. i

4. The combination with a pulverizing mill comprising a high speed rotor having a plurality cent the axis of rotation of the rotor and having outlet openings in its peripheral wall for the es- ,cape oi the pulverized material; of means for 7 cent the axis oi. rotation of the rotor and hav feeding material to be pulverized to the mill chamber at a controlled rate comprising a hoptric with said discharge opening and spaced from the hopper bottom sufllciently to permit the material to pass beneath it, and means providing a suction passage leading from the discharge opening of. the hopper to the feed opening of the mill I chamber v 5. The combination with a pulverizing mill comprising a high speed rotor having a plurality,

oi circumferentially spaced beaters mounted within a chamber having a feed opening adiaing outlet openings in its peripheral wall for the escape of the pulverizedmaterial; of means for feeding material to be,pulverlzedito the mill chamber at a controlled rate comprising a hopper for receiving the material having a bottom ing and spaced from the hopperbottomfsufliciently .to permit the material topass beneath it, a deflector circular in cross-section mounted centrally within the outlet end ot the air, pipe providing a restricted annular air outlet, and means providing a suction passage leading from the discharge opening of the hopper to the feed opening of the mill chamber. 1

6. E A pulverizing mill as claimed in claim 5 in which the deflector is a vertically adjustable cone.

:WILLIAM M. SHELDON. 

